Asymmetric Molecular Dynamics and Anisotropic Phase Separation in the Cocrystal of the Crystalline/Crystalline Polymer Blend

Zheng, Ying; Kafle, Navin; Schwarz, Derek; Eagan, James M.; Hayano, Shigetaka; Nakama, Yuki; Pan, Pengju; Miyoshi, Toshikazu

doi:10.1021/acsmacrolett.1c00745

Abstract

The layered semiconductor In₂Se₃has a low temperature crystalline–crystalline (α → β) phase transformation with distinct electrical properties that make it a promising candidate for phase change memory. Here, using scanning tunneling microscopy, correlative in situ micro‐Raman, and electrical measurements, it is shown that the β phase can persist in bulk crystals at room temperature in non‐oxidative environments. Of particular note, the stability of β phase crystals in ambient conditions under encapsulation of graphene and similar passivation layers, is reported for the first time. The strategy of encapsulation to ensure the persistence of β phase overlaps with efforts to passivate switching materials. It is further demonstrated that degradation from the elevated temperatures required for the phase change is slowed through examination of Raman signatures. These results demonstrate an alternative method of phase manipulation with a new stabilization of β‐In₂Se₃in ambient conditions potentially extendable to other polymorphic materials, and the importance of passivation in In₂Se₃memory devices.

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